Rotary compressor

ABSTRACT

A rotary compressor for which a refrigerant compression capacity is varied between plural stages is provided. The rotary compressor has a rotating shaft, a reversible motor to rotate the rotating shaft in a first or a second direction, first and second compression chambers in which a refrigerant compression stroke and an idle stroke are alternately performed in accordance with a rotating direction of the rotating shaft, a first sub-path allowing a predetermined point of the first compression chamber to communicate with a refrigerant intake side of the first compression chamber to control a compression capacity of the first compression chamber, a second sub-path allowing a predetermined point of the second compression chamber to communicate with a refrigerant intake side of the second compression chamber to control a compression capacity of the second compression chamber, and a path control unit to control opening ratios of the first and second sub-paths.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of Korean Application No.2003-17994, filed Mar. 22, 2003, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates, in general, to rotary compressorsand, more particularly, to a variable capacity rotary compressor whichhas two compression chambers so as to alternately perform a refrigerantcompression stroke and an idle stroke in the two compression chambers inaccordance with a change in a rotating direction of a rotating shaft.

[0004] 2. Description of the Related Art

[0005] As is well known to those skilled in the art, a rotary compressoris used as a refrigerant compression unit in a refrigerant circulationcircuit of a refrigerating system, such as an air conditioner, a heater,or a refrigerator which controls a temperature of air in a desiredspace. In the refrigerant circulation circuit, the rotary compressorsucks, compresses and discharges the refrigerant.

[0006] A refrigerant compression capacity of the rotary compressor maybe controlled in accordance with a change in conditions of a targetspace. The rotary compressors are provided such that the refrigerantcompression capacity thereof is controllable, are so-called “variablecapacity rotary compressors”. Particularly in a case of multiunit airconditioners each having several indoor units operated in conjunctionwith one outdoor unit, use of the variable capacity compressors isnecessary. In the related art, the variable capacity of the rotarycompressors is accomplished by use of electronic elements, such asinverter motors or blushless direct current (BLDC) motors, incompressors. The electronic elements electronically control a capacityof the rotary compressors.

[0007] However, the variable capacity rotary compressors having theinverter motors or the BLDC motors are problematic in that to usecontrol circuit boards to control an operation of the inverter motors orthe BLDC motors is necessary, thus increasing a production cost of thevariable capacity rotary compressors due to the control circuit boardsbeing expensive. Further, due to electric power consumption of thecontrol circuit boards, the power consumption of the variable capacityrotary compressors is undesirably increased. In an effort to overcomethe problems experienced in the conventional variable capacity rotarycompressors having the electronic elements, such as the inverter motorsor the BLDC motors, the inventors of the present invention proposed arotary compressor, the refrigerant compression capacity of which isvaried as desired between two stages by use of a mechanical mechanism.

SUMMARY OF THE INVENTION

[0008] Accordingly, it is an aspect of the present invention to providea variable capacity rotary compressor of which a refrigerant compressioncapacity is varied as desired between four stages by use of a mechanicalmechanism.

[0009] Additional aspects and/or advantages of the invention will be setforth in part in the description which follows and, in part, will beobvious from the description, or may be learned by practice of theinvention.

[0010] The above and/or other aspects of the present invention areachieved by providing a rotary compressor, having a rotating shaftcomprising first and second eccentric parts; a reversible motor torotate the rotating shaft in a first direction or a second direction; afirst cylinder comprising a first compression chamber in which arefrigerant compression stroke or an idle stroke is performed inaccordance with a rotating direction of the first eccentric part of therotating shaft; a first intake port to suck a refrigerant into the firstcompression chamber; and a first exhaust port to discharge therefrigerant from the first compression chamber after the refrigerant iscompressed; a second cylinder comprising a second compression chamber inwhich the refrigerant compression stroke or the idle stroke is performedin accordance with the rotating direction of the second eccentric partof the rotating shaft, such that first and second compression chambersalternately perform the compression stroke and the idle stroke; a secondintake port to suck the refrigerant into the second compression chamber;and a second exhaust port to discharge the refrigerant from the secondcompression chamber after the refrigerant is compressed; a firstsub-path which allows a predetermined point of the first compressionchamber to communicate with the first intake port so as to control acompression capacity of the first compression chamber; and a pathcontrol unit to control an opening ratio of the first sub-path.

[0011] In the rotary compressor, the first sub-path is a first sub-pathpipe provided to allow the predetermined point of the first compressionchamber to communicate with the first intake port, or a first sub-pathgroove provided in the first cylinder to allow the predetermined pointof the first compression chamber to communicate with the first intakeport.

[0012] The rotary compressor further comprises a second sub-path whichallows a predetermined point of the second compression chamber tocommunicate with the second intake port so as to control a compressioncapacity of the second compression chamber, an opening ratio of thesecond sub-path being controlled by the path control unit.

[0013] In the rotary compressor, the second sub-path is a secondsub-path pipe provided to allow the predetermined point of the secondcompression chamber to communicate with the second intake port, or asecond sub-path groove provided in the second cylinder to allow thepredetermined point of the second compression chamber to communicatewith the second intake port.

[0014] In the rotary compressor, the path control unit includes firstand second path control units which control opening ratios of the firstand second sub-paths, respectively.

[0015] The first and second compression chambers have differentcompression capacities.

[0016] The above and/or other aspects are achieved by providing a rotarycompressor, having a rotating shaft; a reversible motor to rotate therotating shaft in a first direction or a second direction; first andsecond compression chambers in which a refrigerant compression strokeand an idle stroke are alternately performed in accordance with arotating direction of the rotating shaft; a first sub-path which allowsa predetermined point of the first compression chamber to communicatewith a refrigerant intake side of the first compression chamber so as tocontrol a compression capacity of the first compression chamber; asecond sub-path which allows a predetermined point of the secondcompression chamber to communicate with a refrigerant intake side of thesecond compression chamber so as to control a compression capacity ofthe second compression chamber; and a path control unit to controlopening ratios of the first and second sub-paths.

[0017] In the rotary compressor, a capacity ratio of the first andsecond compression chambers in a range of about is 2.1:1 to 1.9:1.

[0018] The predetermined point of the first compression chamber isdetermined such that a compression capacity of the first compressionchamber, in a state that the first sub-path is opened by the pathcontrol unit, is reduced by about 20% to 30%, in comparison with thecompression capacity of the first compression chamber in a state thatthe first sub-path is closed.

[0019] The predetermined point of the second compression chamber isdetermined such that a compression capacity of the second compressionchamber, in a state that the second sub-path is opened by the pathcontrol unit, is reduced by about 40% to 60%, in comparison with thecompression capacity of the second compression chamber in a state thatthe second sub-path is closed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and/or other aspects and advantages of the invention willbecome apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

[0021]FIG. 1 is a longitudinal sectional view of a variable capacityrotary compressor, according to a first embodiment of the presentinvention;

[0022]FIG. 2 is a perspective view of a compression unit of the rotarycompressor of FIG. 1;

[0023]FIG. 3 is an exploded perspective view of the compression unit ofFIG. 2;

[0024]FIGS. 4 and 5 are latitudinal sectional views taken along the lineI-I showing and operation of the rotary compressor of FIG. 1;

[0025]FIGS. 6 and 7 are latitudinal sectional views taken along the lineII-II showing an operation of the rotary compressor of FIG. 1; and

[0026]FIG. 8 is a latitudinal sectional view of a variable capacityrotary compressor, according to a second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Reference will now be made in detail to the present preferredembodiments of the present invention, examples of which are illustratedin the accompanying drawings, wherein like reference numerals refer tolike elements throughout.

[0028]FIG. 1 is a longitudinal sectioned view of a variable capacityrotary compressor, according to a first embodiment of the presentinvention. FIG. 2 is a perspective view of a compression unit of therotary compressor of FIG. 1. FIG. 3 is an exploded perspective view ofthe compression unit of FIG. 2.

[0029] As shown in FIGS. 1 to 3, the variable capacity rotary compressor1 according to the first embodiment of the present invention includes ahermetic casing 100, with a drive unit 200 and a compression unit 300installed in the hermetic casing 100. The drive unit 200 generates arotating force when an electric current is applied to the drive unit200. The compression unit 300 is coupled to the drive unit 200 through arotating shaft 21 so as to compress refrigerant by the rotating force ofthe drive unit 200.

[0030] The drive unit 200 includes the rotating shaft 21 having firstand second eccentric parts 21 a and 21 b. The drive unit 200 alsoincludes a rotor 22 and a stator 23. The rotor 22 is a cylindrical bodyfitted over an upper portion of the rotating shaft 21 toelectromagnetically rotate in cooperation with the stator 23. The stator23 is fixed to an inner surface of the hermetic casing 100 whilesurrounding the rotor 22, with an annular gap defined between the rotor22 and the stator 23. The stator 23 is wound with a coil that isconnected to an external electric power source, so that the stator 23produces a magnetic field to electromagnetically rotate the rotor 22. Inthe drive unit 200, the rotor 22 and the stator 23 comprise a reversibledrive motor that is rotatable in either a clockwise direction or acounter clockwise direction.

[0031] The compression unit 300 includes first and second cylinders 31and 32. The first cylinder 31 defines therein a first compressionchamber 31 a which receives the first eccentric part 21 a of therotating shaft 21 therein so as to perform a compression stroke during aforward rotation of the rotating shaft 21, and an idle stroke during areverse rotation of the rotating shaft 21. The second cylinder 32defines therein a second compression chamber 32 a which receives thesecond eccentric part 21 b of the rotating shaft 21 therein and has acompression capacity smaller than that of the first compression chamber31 a (about a half of the compression capacity of that of the firstcompression chamber 31 a). The second compression chamber 32 a performsan idle stroke during the forward rotation of the rotating shaft 21, anda compression stroke during the reverse rotation of the rotating shaft21. The first and second compression chambers 31 a and 32 a thusalternately perform the compression and idle strokes. A first rollerpiston 33 is fitted over the first eccentric part 21 a of the rotatingshaft 21 in the first compression chamber 31 a, a predetermined firstgap defined between the first roller piston 33 and the first eccentricpart 21 a to be eccentric to a side. A second roller piston 34 is fittedover the second eccentric part 21 b of the rotating shaft 21 in thesecond compression chamber 32 a, a predetermined second gap definedbetween the second roller piston 34 and the second eccentric part 21 bto be eccentric to another side. A first cam bush 35 having an eccentricshape is fitted in the first eccentric gap between the first eccentricpart 21 a and the first roller piston 33 in the first compressionchamber 31 a. A second cam bush 36 having an eccentric shape is fittedin the second eccentric gap between the second eccentric part 21 b andthe second roller piston 34 in the second compression chamber 32 a. Anupper flange 37 hermetically seals an upper end of the first compressionchamber 31 a while supporting an intermediate portion of the rotatingshaft 21. An intermediate plate 38 is provided between the first andsecond cylinders 31 and 32 so as to hermetically seal both a lower endof the first compression chamber 31 a and an upper end of the secondcompression chamber 32 a. A lower flange 39 hermetically seals a lowerend of the second compression chamber 32 a while supporting a lower endof the rotating shaft 21.

[0032] During the forward rotation of the rotating shaft 21, the firstcam bush 35 causes an eccentric rotation of the first roller piston 33to allow the compression stroke to be performed in the first compressionchamber 31 a. However, during the reverse rotation of the rotating shaft21, the first cam bush 35 causes a concentric rotation of the firstroller piston 33 to allow the idle stroke to be performed in the firstcompression chamber 31 a. The second cam bush 36 causes a concentricrotation of the second roller piston 34 during the forward rotation ofthe rotating shaft 21 to allow the idle stroke to be performed in thesecond compression chamber 32 a. However, during the reverse rotation ofthe rotating shaft 21, the second cam bush 36 causes an eccentricrotation of the second roller piston 34 to allow the compression stroketo be performed in the second compression chamber 32 a.

[0033] The first cylinder 31 has a first intake port 31 b, a firstexhaust port 31 c, and a first sub-path groove 31 d. The first intakeport 31 b sucks the refrigerant into the first compression chamber 31 a,while the first exhaust port 31 c discharges the refrigerant from thefirst compression chamber 31 a after the refrigerant is compressed. Thefirst sub-path groove 31 d forms a first sub-path, which allows thefirst intake port 31 b to communicate with a point “A” of the firstcompression chamber 31 a, so as to control a capacity of the firstcompression chamber 31 a. In a same manner, the second cylinder 32 has asecond intake port 32 b, a second exhaust port 32 c, and a secondsub-path groove 32 d. The second intake port 32 b sucks the refrigerantinto the second compression chamber 32 a, while the second exhaust port32 c discharges the refrigerant from the second compression chamber 32 aafter the refrigerant is compressed. The second sub-path groove 32 dforms a second sub-path which allows the second intake port 32 b tocommunicate with a point “B” of the second compression chamber 32 a soas to control a capacity of the second compression chamber 32 a.

[0034] The variable capacity rotary compressor has a path control unitdriven by a solenoid unit to control opening ratios of the first andsecond sub-path grooves 31 d and 32 d. As shown in FIGS. 2 and 3, thepath control unit is fabricated as two separate units, first and secondpath control units 40 a and 40 b which separately control the openingratios of the first and second sub-path grooves 31 d and 32 d. The firstpath control unit 40 a controls the opening ratio of the first sub-pathgroove 31 d and the second path control unit 40 b controls the openingratio of the second sub-path groove 32 d. However, the path control unitmay be a single unit that controls the opening ratios of both of thefirst and second sub-path grooves 31 d and 32 d.

[0035] A capacity ratio of the first, second, third and fourth stages ofthe variable capacity rotary compressor 1 may be set to, for example,4:3:2:1, and to accomplish the capacity ratio of 4:3:2:1 of the fourstages, the first and second compression chambers 31 a and 31 b have acapacity ratio of 2:1. However, the capacity ratio of the first, second,third and fourth stages of the variable capacity rotary compressor 1 andthe capacity ratio of the first and second compression chambers 31 a and32 a may change from the above-mentioned ratios if the variable capacityrotary compressor 1 varies in a refrigerant compression capacity thereofbetween the four stages. When the capacity ratio of the first, second,third and fourth stages of the variable capacity rotary compressor 1 isset to 4:3:2:1, as described above, the capacity ratio of the first andsecond compression chambers 31 a and 31 b may be set in a range of about2.1:1 to 1.9:1, in consideration of machining allowances and otherconditions of the variable capacity rotary compressor 1.

[0036] To produce the variable capacity rotary compressor 1 having thecapacity ratio of the first, second, third and fourth stages set to4:3:2:1, the point “A” in the first compression chamber 31 a isdetermined as follows. The point “A” in the first compression chamber 31a is determined such that when the first sub-path groove 31 d is openedunder the control of the first path control unit 40 a, a variablecapacity of the first compression chamber 31 a is reduced by 25%,compared with a capacity of the first compression chamber 31 a in astate that the first sub-path groove 31 d is closed. However, a capacityreduction ratio of the first compression chamber 31 a may change fromthe above-mentioned ratio, if the changed capacity reduction ratio ofthe first compression chamber 31 a allows the rotary compressor to varyin a capacity thereof between the first to fourth stages. When thecapacity ratio of the first, second, third and fourth stages of thevariable capacity rotary compressor 1 is set to 4:3:2:1, as describedabove, the point “A” in the first compression chamber 31 a may bedetermined such that the variable capacity of the first compressionchamber 31 a, in a state that the first sub-path groove 31 d is opened,is reduced in a range of about 20% to 30%, compared with the capacity ofthe first compression chamber 31 a in the state that the first sub-pathgroove 31 d is closed.

[0037] To produce the variable capacity rotary compressor 1 having thecapacity ratio of the second to fourth stages set to 4:3:2:1, the point“B” in the second compression chamber 32 a is determined as follows. Thepoint “B” in the second compression chamber 32 a is determined such thatwhen the second sub-path groove 32 d is opened under the control of thesecond path control unit 40 b, a variable capacity of the secondcompression chamber 32 a is reduced by 50% compared with the capacity ofthe second compression chamber 32 a in a state that the second sub-pathgroove 32 d is closed. However, a capacity reduction ratio of the secondcompression chamber 32 a may change from the above-mentioned ratio, ifthe changed capacity reduction ratio of the second compression chamber32 a allows the rotary compressor to vary in a capacity thereof betweenthe first to fourth stages. When the capacity ratio of the first,second, third and fourth stages of the variable capacity rotarycompressor 1 is set to 4:3:2:1, as described above, the point “B” in thesecond compression chamber 32 a may be determined such that the variablecapacity of the second compression chamber 32 a, in a state that thesecond sub-path groove 32 d, is opened is reduced in a range of about40% to 60%, in comparison with the capacity of the second compressionchamber 32 a in the state that the second sub-path groove 32 d isclosed.

[0038] The operation and effect of the variable capacity rotarycompressor having the above-mentioned construction will be describedherein below.

[0039] The variable capacity rotary compressor 1 is used as arefrigerant compression unit in a refrigerant circulation circuit of arefrigerating system, such as an air conditioner, a heater, or arefrigerator that controls a temperature of air in a target space.

[0040] To appropriately and effectively control the temperature of airin the target space, the refrigerant compression capacity of the rotarycompressor is required to change in accordance with the presenttemperature of the space.

[0041] The variable capacity rotary compressor 1 is operated as followsin the first to fourth stage modes wherein the rotary compressorachieves different compression capacities, and stage numbers of thevariable capacity rotary compressor 1 in the following description aredesignated in order of a scale of the capacities from a largest capacityto a smallest capacity.

[0042] 1. Operation of the Variable Capacity Rotary Compressor 1 in aFirst Stage Mode

[0043] In a first stage mode, the reversible motor of the drive unit 200rotates the rotating shaft 21 in a forward direction, as shown in FIG.4, so that the first roller piston 33 eccentrically rotates by anoperation of both the first eccentric part 21 a of the rotating shaft 21and the first cam bush 35. The first roller piston 33 in the first stagemode performs a compression stroke in the first compression chamber 31a, while the second roller piston 34 in the first stage modeconcentrically rotates to perform an idle stroke in the secondcompression chamber 32 a. In the first stage mode, the first pathcontrol unit 40 a closes the first sub-path groove 31 d, and thevariable capacity rotary compressor 1 achieves a largest refrigerantcompression capacity in the first stage mode.

[0044] 2. Operation of the Variable Capacity Rotary Compressor 1 in theSecond Stage Mode

[0045] In the second stage mode, the reversible motor of the drive unit200 rotates the rotating shaft 21 in the forward direction, as shown inFIG. 5, so that the first roller piston 33 eccentrically rotates by theoperation of both the first eccentric part 21 a of the rotating shaft 21and the first cam bush 35. The first roller piston 33 performs thecompression stroke in the first compression chamber 31 a, while thesecond roller piston 34 concentrically rotates to perform the idlestroke in the second compression chamber 32 a, in a same manner as thatdescribed for the first stage mode. However, in the second stage modedifferent from in the first stage mode, the first path control unit 40 aopens the first sub-path groove 31 d, so that an effective refrigerantcompression stroke performed by the first roller piston 33 in the firstcompression chamber 31 a starts at the point “A” of the firstcompression chamber 31 a. The variable capacity rotary compressor 1 inthe second stage mode achieves a compression capacity equal to 75% ofthe capacity expected in the first stage mode.

[0046] 3. Operation of the Variable Capacity Rotary Compressor 1 in theThird Stage Mode

[0047] In the third stage mode, the reversible motor of the drive unit200 rotates the rotating shaft 21 in a reverse direction, as shown inFIG. 6, so that the first roller piston 33 concentrically rotates toperform the idle stroke in the first compression chamber 31 a. However,in the second compression chamber 32 a during the third stage mode, thesecond roller piston 34 eccentrically rotates by an operation of boththe second eccentric part 21 b of the rotating shaft 21 and the secondcam bush 36. The second roller piston 34 performs the compression strokein the second compression chamber 32 a. The second path control unit 40b in the third stage mode closes the second sub-path groove 32 d, sothat the variable capacity rotary compressor 1 in the third stage modeachieves the compression capacity which is equal to 50% of the capacityexpected in the first stage mode, and which is equal to 75% of thecapacity expected in the second stage mode.

[0048] 4. Operation of the Variable Capacity Rotary Compressor 1 in aFourth Stage Mode

[0049] In the fourth stage mode, the reversible motor of the drive unit200 rotates the rotating shaft 21 in the reverse direction, as shown inFIG. 7, so that the first roller piston 33 concentrically rotates toperform the idle stroke in the first compression chamber 31 a, while thesecond roller piston 34 eccentrically rotates by the operation of boththe second eccentric part 21 b of the rotating shaft 21 and the secondcam bush 36. The second roller piston 34 performs the compression strokein the second compression chamber 32 a, in a same manner as thatdescribed for the third stage mode. However, in the fourth stage modewhich is different from in the third stage mode, the second path controlunit 40 b opens the second sub-path groove 32 d, so that the effectiverefrigerant compression stroke performed by the second roller piston 34in the second compression chamber 32 a starts at the point “B” of thesecond compression chamber 32 a. The variable capacity rotary compressor1 in the fourth stage mode achieves a compression capacity that is equalto 25% of the capacity expected in the first stage mode, that is equalto 33% of the capacity expected in the second stage mode, and that isequal to 50% of the capacity expected in the third stage mode.

[0050] As described above, the variable capacity rotary compressor 1varies in the refrigerant compression capacity thereof between the fourstages such that the first to fourth stages have a capacity ratio of4:3:2:1. The capacity ratio of the first, second, third and fourthstages of the variable capacity rotary compressor 1 is not limited tothe above-mentioned ratio, but may be set to any other ratio withoutaffecting an operation of the present invention.

[0051]FIG. 8 is a latitudinal sectioned view of a variable capacityrotary compressor 2, according to a second embodiment of the presentinvention. As shown in FIG. 8, the second embodiment alters aconstruction of the first and second sub-paths and the first and secondpath control units provided in the variable capacity rotary compressor 2to control a refrigerant compression capacities of the first and secondcompression chambers 31 a and 32 a. That is, the first and secondsub-paths are, respectively, formed by a first sub-path pipe 51 a whichallows the first compression chamber 31 a to communicate with the firstintake port 31 b, and a second sub-path pipe 51 b which allows thesecond compression chamber 32 a to communicate with the second intakeport 32 b. To control opening ratios of the first and second sub-pathpipes 51 a and 51 b, the first and second path control units 50 a and 50b are provided in the variable capacity rotary compressor 2.

[0052] As described above, the variable capacity rotary compressor whichvaries in the refrigerant compression capacity thereof as desiredbetween four stages such that first to fourth stages by use of amechanical mechanism, so that the variable capacity rotary compressor 2may be used in a refrigerating system, such as an air conditioner(particularly, a multiunit air conditioner), a heater, or a refrigeratorrequired to be equipped with a variable capacity compressor.

[0053] In addition, the variable capacity rotary compressor does notneed an expensive control circuit board which must be used inconventional electronically controlled variable capacity compressors tocontrol an operation of an inverter motor or a BLDC motor. The variablecapacity rotary compressor reduces a production cost of the variablecapacity rotary compressors.

[0054] Furthermore, the variable capacity rotary compressor may reducepower consumption compared with the conventional electronicallycontrolled variable capacity compressors.

[0055] Although a few preferred embodiments of the present inventionhave been shown and described, it would be appreciated by those skilledin the art that changes may be made in these embodiments withoutdeparting from the principles and spirit of the invention, the scope ofwhich is defined in the claims and their equivalents. For example, therotary compressor of the present invention may be provided with only oneof the first and second sub-paths. In such a case, the capacity of therotary compressor is varied between three stages, that is, first tothird stages.

What is claimed is:
 1. A rotary compressor, comprising: a rotating shaft having first and second eccentric parts; a reversible motor to rotate the rotating shaft in either a first rotating direction or a second rotating direction; a first cylinder comprising: a first compression chamber in which a refrigerant compression stroke or an idle stroke is performed in accordance with the first or second rotating direction of the first eccentric part of the rotating shaft; a first intake port to suck a refrigerant into the first compression chamber; and a first exhaust port to discharge the refrigerant from the first compression chamber after the refrigerant is compressed; a second cylinder comprising: a second compression chamber in which the refrigerant compression stroke or the idle stroke is performed in accordance with the first or second rotating direction of the second eccentric part of the rotating shaft, such that first and second compression chambers alternately perform the compression stroke and the idle stroke; a second intake port to suck the refrigerant into the second compression chamber; and a second exhaust port to discharge the refrigerant from the second compression chamber after the refrigerant is compressed; a first sub-path which allows a predetermined point of the first compression chamber to communicate with the first intake port so as to control a compression capacity of the first compression chamber; and a path control unit to control an opening ratio of the first sub-path.
 2. The rotary compressor according to claim 1, wherein the first sub-path comprises: a first sub-path pipe provided to allow the predetermined point of the first compression chamber to communicate with the first intake port, or a first sub-path groove provided in the first cylinder to allow the predetermined point of the first compression chamber to communicate with the first intake port.
 3. The rotary compressor according to claim 1, further comprising: a second sub-path which allows a predetermined point of the second compression chamber to communicate with the second intake port so as to control a compression capacity of the second compression chamber, the second sub-path being controlled in an opening ratio thereof by the path control unit.
 4. The rotary compressor according to claim 3, wherein the second sub-path comprises: a second sub-path pipe provided to allow the predetermined point of the second compression chamber to communicate with the second intake port, or a second sub-path groove provided in the second cylinder to allow the predetermined point of the second compression chamber to communicate with the second intake port.
 5. The rotary compressor according to claim 3, wherein the path control unit comprises: first and second path control units which control the opening ratios of the first and second sub-paths, respectively.
 6. The rotary compressor according to claim 1, wherein the first and second compression chambers have different compression capacities.
 7. A rotary compressor, comprising: a rotating shaft; a reversible motor to rotate the rotating shaft in either a first rotating direction or a second rotating direction; first and second compression chambers in which a refrigerant compression stroke and an idle stroke are alternately performed in accordance with the first rotating direction or second rotating direction of the rotating shaft; a first sub-path which allows a predetermined point of the first compression chamber to communicate with a refrigerant intake side of the first compression chamber so as to control a compression capacity of the first compression chamber; a second sub-path which allows a predetermined point of the second compression chamber to communicate with a refrigerant intake side of the second compression chamber so as to control a compression capacity of the second compression chamber; and a path control unit to control opening ratios of the first and second sub-paths.
 8. The rotary compressor according to claim 7, wherein a capacity ratio of the first and second compression chambers is in a range of 2.1:1 to 1.9:1.
 9. The rotary compressor according to claim 7, wherein the predetermined point of the first compression chamber is determined such that the compression capacity of the first compression chamber, in a state that the first sub-path is opened by the path control unit, is reduced in a range of 20% to 30% compared with the compression capacity of the first compression chamber in a state that the first sub-path is closed.
 10. The rotary compressor according to claim 7, wherein the predetermined point of the second compression chamber is determined such that the compression capacity of the second compression chamber, in a state that the second sub-path is opened by the path control unit, is reduced in a range of 40% to 60% compared with the compression capacity of the second compression chamber in a state that the second sub-path is closed.
 11. A rotary compressor, comprising: a rotating shaft having first and second eccentric parts which rotate thereby; a first compression chamber in which a refrigerant compression stroke or an idle stroke is performed in accordance with a first rotating direction or a second rotating direction of the first eccentric part of the rotating shaft to selectively compress a refrigerant in the first compression chamber; a second compression chamber in which the refrigerant compression stroke or the idle stroke is performed in accordance with the first rotating direction or the second rotating direction of the second eccentric part of the rotating shaft to selectively compress a refrigerant in the second compression chamber, such that first and second compression chambers alternately perform the refrigerant compression stroke and the idle stroke; and a compression capacity controller to control a compression of the first compression chamber.
 12. The rotary compressor according to claim 11, wherein: the compression capacity controller comprises: a first sub-path, and a path control unit to control an opening ratio of the first sub-path the first compression chamber comprises a first intake port to suck the refrigerant into the first compression chamber, the first sub-path allowing a predetermined point of the first compression chamber to connect to the first intake port.
 13. The rotary compressor according to claim 12, wherein the first sub-path comprises a first sub-path connector connectable with the predetermined point of the first compression chamber and the first intake port.
 14. The rotary compressor according to claim 12, wherein: the compression capacity controller further comprises a second sub-path controlled in an opening ratio thereof by the path control unit; and the second compression chamber comprises a second intake port to suck the refrigerant into the second compression chamber, the second sub-path allowing a predetermined point of the second compression chamber to connect to the second intake port so as to control a compression capacity of the second compression chamber.
 15. The rotary compressor according to claim 14, wherein the second sub-path comprises a second sub-path connector connectable with the predetermined point of the second compression chamber and the second intake port.
 16. The rotary compressor according to claim 14, wherein the path control unit comprises first and second path control units which control the opening ratios of the first and second sub-paths, respectively.
 17. The rotary compressor according to claim 11, wherein the first and second compression chambers have different compression capacities from each other.
 18. The rotary compressor according to claim 11, wherein the second compression chamber has a compression capacity smaller than that of the first compression chamber.
 19. The rotary compressor according to claim 11, wherein the second compression chamber has a compression capacity about a half of a compression capacity of the first compression chamber.
 20. The rotary compressor according to claim 11, further comprising: a first roller piston fitting over the first eccentric part of the rotating shaft in the first compression chamber; a first gap defined between the first roller piston and the first eccentric part, and eccentric in a shape thereof; and a first cam bush having an eccentric shape and fitting in the first eccentric gap between the first eccentric part and the first roller piston in the first compression chamber.
 21. The rotary compressor according to claim 20, wherein, when the rotating shaft rotates in the first rotating direction, the first cam bush causes an eccentric rotation of the first roller piston to perform the compression stroke in the first compression chamber.
 22. The rotary compressor according to claim 20, wherein, when the rotating shaft rotates in the second rotating direction, the first cam bush causes a concentric rotation of the first roller piston to perform the idle stroke in the first compression chamber.
 23. The rotary compressor according to claim 20, further comprising: a second roller piston fitting over the second eccentric part of the rotating shaft in the second compression chamber; a second gap defined between the second roller piston and the second eccentric part, and eccentric in a shape thereof; and a second cam bush having an eccentric shape and fitting in the second eccentric gap between the second eccentric part and the second roller piston in the second compression chamber.
 24. The rotary compressor according to claim 23, wherein, when the rotating shaft rotates in the second rotating direction, the second cam bush causes an eccentric rotation of the second roller piston to perform the compression stroke in the second compression chamber.
 25. The rotary compressor according to claim 23, wherein, when the rotating shaft rotates in the first rotating direction, the second cam bush causes a concentric rotation of the second roller piston to perform the idle stroke in the second compression chamber.
 26. The rotary compressor according to claim 14, wherein a capacity ratio of the rotary compressor is settable based on the opening ratios of the first and second sub-paths within a range of 4:1.
 27. A rotary compressor, comprising: a rotating shaft rotating therein; first and second compression chambers in which a refrigerant compression stroke and an idle stroke are alternately performed in accordance with a first rotating direction or a second rotating direction of the rotating shaft; one or more sub-paths to connect one or more predetermined points of respective one or ones of the first and second compression chambers to respective one or ones of a refrigerant intake side of the first and second compression chambers so as to control respective one or ones of compression capacities of the first and second compression chambers; and a path control unit to control opening ratios of the one or more sub-paths.
 28. The rotary compressor according to claim 27, wherein a capacity ratio of the first and second compression chambers is in a range of 2.1:1 to 1.9:1.
 29. The rotary compressor according to claim 27, wherein a respective predetermined point of the first compression chamber is determined such that the compression capacity of the first compression chamber, in a state that one sub-path, corresponding to the first compression chamber, is opened by the path control unit, is reduced in a range of 20% to 30% compared with the compression capacity of the first compression chamber in a state that the one sub-path is closed.
 30. The rotary compressor according to claim 27, wherein a respective predetermined point of the second compression chamber is determined such that the compression capacity of the second compression chamber, in a state that a further sub-path, corresponding to the second compression chamber, is opened by the path control unit, is reduced in a range of 40% to 60% compared with the compression capacity of the second compression chamber in a state that the further sub-path is closed.
 31. A rotary compressor, comprising: a rotating shaft rotating therein; plural compression chambers in which a refrigerant compression stroke and an idle stroke are performed in accordance with a first rotating direction or second rotating direction of the rotating shaft; one or more sub-paths to connect one or more predetermined points of respective one or ones of the plural compression chambers to a refrigerant intake side of the plural compression chambers so as to control respective one or ones of compression capacities of the plural compression chambers; and a path control unit to control opening ratios of the one or more sub-paths.
 32. A rotary compressor, comprising: plural compression chambers in which a refrigerant compression stroke and an idle stroke are performed in accordance with a first rotating direction or second rotating direction of the rotating shaft; and one or more sub-paths, respectively, connectable to the plural compression chambers to vary a refrigerant compression capacity thereof to set a total capacity of the rotary compressor between at least four stages based on a direction of a rotation of the rotating shaft and a connection status of each of the one or more sub-paths.
 33. A method of operating a rotary compressor having a rotating shaft with first and second eccentric parts to rotate thereby, first and second compression chambers in which a refrigerant compression stroke or an idle stroke is performed in accordance with a rotating direction of the first and second eccentric part, respectively, the first and second compression chambers, alternately, performing the compression stroke and the idle stroke, and first and second sub-paths, respectively, allowing a predetermined point of the first and second compression chambers to connect to a intake side of the rotary compressor, comprising: when operating in a first stage, in which the rotating shaft rotates in a first direction, performing the compression stroke in the first compression chamber, while performing the idle stroke in the second compression chamber and closing a first sub-path to maximize a compression capacity of the rotary compressor; when operating in a second stage, in which the rotating shaft rotates in a first direction, performing the compression stroke in the first compression chamber, while performing the idle stroke in the second compression chamber and opening a first sub-path to reduce the compression capacity of the rotary compressor by about 25% from that of the compression capacity of the rotary compressor operating in the first stage; when operating in a third stage, in which the rotating shaft rotates in a second direction, performing the idle stroke in the first compression chamber, while performing the compression stroke in the second compression chamber and closing the second sub-path to reduce the compression capacity of the rotary compressor by about 50% from that of the compression capacity of the rotary compressor operating in the first stage; and when operating in a fourth stage, in which the rotating shaft rotates in the second direction, performing the idle stroke in the first compression chamber, while performing the compression stroke in the second compression chamber and opening the second sub-path to reduce the compression capacity of the rotary compressor by about 75% from that of the compression capacity of the rotary compressor operating in the first stage. 